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Multi Section Digital Axle Counter MSDAC 730


The Multi Section Digital Axle Counter MSDAC 730 is a Signaling equipment for simultaneous detection of track vacancy for several lines in a station or yard area including point zone sections. The MSDAC system can be configured up to 40 detection points specific to the station / yard. The system provides the individual vital relay output for each section / point zone based on the principle of counting of axles. The system can be deployed for simultaneous monitoring of following track sections in a station or yard area.

The application of the system for simultaneous monitoring includes:

1. Loop Line 5. Common Line
2. Main Line 6. StabLing Line
3. Platform Line 7. Point Zone
4. Goods Line 8. Dead End

Brief of System
  1. Axle Detectors
  2. Electronic field units
  3. Central Evaluator
  4. SM's Reset panel
  5. Monitoring Unit.
Click for Demo

The Central Evaluator of the system has been designed and developed with ModularStructure (5 sets of cards). Each set of cards can be connected to minimum 2 nos. and maximum 8 nos. of field units. The complete system with all the 5 sets of cards can be connected to maximum 40 nos. of field units. Therefore, the system has the provision to scale up or scale down according to the requirement at station.

Principle of Working

The Axle Detectors are installed at both limits of a track section along with their electronic field units on track side. Each of them is called a detection point. The total No. of detection points is to be decided by Railways to cover the station area as per total number of track sections to be brought under monitoring by means of MSDAC. The field units are connected with Central Evaluator by means of ½ Quad cable. The Central Evaluator is to be installed in Station / Cabin. The 24V power supply is to be installed at station. The 24V is connected to Central Evaluator and also is to be taken to the field units by means of a separate power cable. The Axle Detectors operates on high frequency (21K Hz & 23K Hz) according to the proven method of electromagnetic wheel detection. When a train wheel enters between the Axle detectors, it influences the electromagnetic field and the wheel is detected. The Axle detectors and the electronics associated with it is working on the principle of Phase Modulation for detection of wheels. A separate small length DC Track circuit is not required for trolley suppression. The detected wheels of a train are converted into pulses and these pulses are counted and stored at the entry and exit field units (fig 3) of the track section. The stored counts as well as its health from the field units are continuously transmitted by means of telegram packets to Central Evaluator on ½ Quad cable. After evaluation of the counts received from entry and exit field units of each section the track "Clear" decision is arrived in Central Evaluator. If the evaluation of counts are equal the Vital Relay (VR) is energized to pick up. Otherwise the VR is dropped and the track section is shown as "Occupied". The contacts of VR is to be provided into signaling circuits of station. The VR for point zone is picked up after evaluating counts from all the field units of that particular section.

Reset Procedure


After failure in the section, it is physically verified and then the Reset command is given from SM's Reset Panel to Central Evaluator (CE). The Reset is then extended to the respective electronic field units on ½ Quad cable which carries data into CE. The section counts are resetted and with the health of field units is normal the section becomes clear. The Central Evaluator, Monitoring unit and Vital Relays are housed in 19" Rack (fig 2). The SM's Reset Panel is a table top model


  1. Trackside Electronic Field Units.
  2. Web type Axle Detectors.
  3. Compatible with 90R,52 kg & 60 kg rail profiles.
  4. Detection of all wheels with diameter > 400 mm.
  5. Track "clear / occupied" for each section through vital relay.
  6. Normal operation during water logging on rails.
  7. Easy to install,commission and maintain.
  8. Monitoring unit for ESM with section wise details


  1. Reliable operation for short detection times.
  2. Immune to traction return currents, electrical and other magnetic disturbance.
  3. MTBF is greater than 15 years.
  4. Operation over temperature range from Zero degree Celsius to +70 degree Celsius for Field units and 0 to +60 degree Celsius for Central Evaluator.


  1. Designed as per CENELEC, SIL- 4 (European standards).
  2. Suitable for connecting maximum of 40 detections.
  3. 21 KHz & 23 KHz High Frequency Phase Modulation type Axle detectors. Virtually maintenance free.
  4. Micro controller based design with 2 out of 2 evaluation in field unit and 2 out of 3 evaluation in Central Evaluator.
  5. Counting of wheel through software.
  6. V.21 modem communication between field unit and Central Evaluator (2 wire).
  7. Opto Isolated Vital Relay Drive for Q type 24V, 1000 ohm.
  8. Protected against the effects of lightning.
  9. High availability through modular design and fault diagnosis via Monitoring Unit near Central Evaluator.
  10. Event Logger for data recording.
  11. Configuration card for entering specific layout of station.


  1. Specification No. RDSO/SPN/176/2002.

Approved by

  1. Submitted for approval to R D S O, LUCKNOW

Development & Field trials

  1. The MSDAC 730 has been indigenously designed & developed by CEL & RDSO under the aegis of DSIR (PATSER SCHEME). The Functional & Fail safety tests was conducted in CEL for all type of train movements. The system was found normal. The system has been installed and is undergoing extensive field trials at Faridabad, N.Rly .
**CEL reserves the right to alter the design or other technical details / parameter with approval from RDSO for improvement of the system .  
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